Benchmark calculations of the shielding constants in the water dimer

The NMR shielding constants in (H2O)(2) have been calculated using GIAO-SCF , MP2, MP4 and CCSD methods and for a range of basis sets. According to the obtained results the 6-311++G** or aug-cc-pVDZ basis sets are recommended for SCF calculations, and the aug-cc-pVXZ series is suggested for correlate d calculations of the interaction-induced changes in the shielding constant s. The counterpoise correction improves the results towards the basis set l imit and is essential in the case of O-17 shielding. Correlation effects ar e substantial for the changes in O-17 shielding, less so for H-1 shielding. They are overestimated by the MP2 method. (C) 2001 Elsevier Science B.V. A ll rights reserved.